1. Field of the Invention
This invention pertains to the field of radio telecommunications generally, and more specifically, to the field of radio telecommunications, cellular and/or wireless personal communications. In particular, it pertains to the provision of a secure wireless party line for radio telecommunications, which is especially useful for mobile cellular and/or personal telecommunications.
2. Description of the Prior Art
This invention pertains to a secure wireless party line system which can be used by a group of wireless mobile radio-telephone users to communicate with each other as though they were connected by a wired party line, but without the cumbersome inconvenience of a long wired tether. The party line function is achieved by the used of a fixed wireless repeater. Each mobile user carries a simple single channel radio transceiver. Spread spectrum transmission is used to provide security and anti-jamming performance.
The party line of conventional wired telephone systems is well known in the prior art, and need not be described in detail. The drawbacks and limitations of the conventional wired party line are also well known. In particular, these drawbacks are dramatically apparent in public events, such as professional sporting events.
Without limiting the generality of the invention of this disclosure, the invention will be described and illustrated with an example from professional sporting events. The outcome of any one of the National Football League (NFL) games carries a tremendously high monetary stake. The way each game is played relies heavily on the instructions from the coaches during the game. Using the wired system 10 illustrated in FIG. 1, the coaches 12, 14, 15 make their decisions on strategy based on the communications received from observers 16, 18 located in a booth 20 high above the playing field 22. These observers 16, 18 have a bird's eye view of all the players on the field 72. There are usually five observers for each team, two on defense 18 and three on offense 16. The communication between the observers 16, 18 high in the booth 20 and the coaches 12, 14, 15 on the playing field 22 is by a dedicated wired party line system 10, as shown in FIG. 1. In this system, the coaches 14 and the observers 16, associated with the offense are connected to one party line 24; and those persons 15, 18 associated with defense are connected to a second party line 26. The head coach 12 can select either one of these two party lines by a switch 28. An identical system is used by the opposing team. The two systems are entirely separate and independent of each other. In a wired party line system, when one person talks, his voice is broadcast to every other person connected to the party line. When several persons are talking at the same time, the individual talker is identified through voice recognition. The coaches 12, 14, 15 on the field communicate with the players, but are confined to move around within a rectangle 40.times.10 yards, as specified by NFL rules. To accommodate his movements, every coach on the field carries a spool of wire with a dedicated assistant to wind and unwind the spool of wire as required by his movement. The major drawback of this system is the wire that each coach must carry and the necessity of winding and unwinding the wire to accommodate the movement of the coach. If there are ten talkers in a given area, there is usually a tangled mess of wires on the ground. This tangled mess of wires not only impedes the movements of the coaches, but also presents a major hazard to the safety of the coaches.
It is highly desirable to replace the two wired party line systems 10 with two secure wireless systems, one for each team. This will eliminate the wires between the field coaches and the wired voice outlets, thus eliminating the tangled mess of wires on the ground. The coaches, who no longer have to worry about being tripped by the wires on the ground, will be able to move freely and expediently in carrying out their instructions to the players.
However, all wireless systems are dedicated systems with one channel for each user. The channels are either separated by frequency as in a frequency division system, or by time as in a time division system, or by code as in a code division system. In order for each user to hear all the other users, he must carry as many radios as there are other users. For instance, if the wireless system is to replace a ten-person party line system, each mobile user must carry nine radios in order to hear and talk to the other nine users at the same time. This is not practical for a portable unit powered by battery.
It is the principal object of this invention to provide a wireless radio-telephone system for party line operation which can operate with only a single radio-telephone for each mobile user.
It is a further object of this invention to provide such a wireless radio-telephone system which is secure and anti-jamming.
It is still a further object of this invention to provide such a secure, wireless radio-telephone party line system which can be used for many communications applications which utilize a patch between wired and wireless telephone users for business purposes or during situations of crisis involving law enforcement, medical, or emergency personnel when several people in different locations must have constant and secure communication with each other.